Thermostatic control



1969 o. a. LEWIS 3,459,163

THERMOSTATIC CONTROL Filed Aug. 22, 1968 56 600mb b? [ea/1's I I 3yATTORNEY United States Patent 3,459,163 THERMOSTATIC CONTROL Donald B.Lewis, Lapeer, Mich., assignor to General Motors Corporation, Detroit,Mich., a corporation of Delaware Filed Aug. 22, 1968, Ser. No. 754,554Int. Cl. F02m 35/04 US. Cl. 123-122 4 Claims ABSTRACT OF THE DISCLOSUREA damped valve member operated by a protected, adjustable bimetallicstrip, contained in a sheet metal body which is further protected by aplastic casing, controls the vacuum signals delivered to a vacuum motorfor positioning a valve which governs the temperature of the inductionair flow delivered through an air cleaner and silencer assembly to aninternal combustion engine.

BACKGROUND OF THE INVENTION Over the years it has been foundadvantageous to control the temperature of the air supplied through theinduction system of an internal combustion engine during certain modesof engine operation. In general, the objects are to improve thevaporization of the fuel delivered into the air stream, thus allowingmore complete combustion of the fuel in the engine combustion chambers,and at the same time to prevent carburetor ring.

The recent systems by which these objects are realized have incorporateda thermostatic control in which a bimetallic strip, mounted on a diecast body, positioned a valve within an orifice plate secured in the diecast body; this control formed vacuum signals appropriate for governingthe induction air flow temperature. Such a construction was subject to anumber of potentially troublesome manufacturing problems and requiredvery rigid production control techniques to assure that the thermostaticcontrol performed accurately. Among such problems were porous castingswhich prevented accurate control over the vacuum signals, intermittentbuzzing or high frequency vibration of the valve member, andinconsistent riveting over of a projection on the die cast body whichsecured the bimetallic strip to the body. In addition, the bimetallicstrip was exposed at the top of the control and, when mounted within theair cleaner housing, was therefore vulnerable to damage during servicingof the air filter element.

It will be appreciated from the foregoing that a desire remained for asimplified design of the thermostatic control which would avoid suchproblems.

SUMMARY OF THE INVENTION A thermostatic control design which satisfiesthis desire is disclosed herein. This design incorporates a body formedof sheet metal stampings. A bimetallic strip is clamped between the bodyand an overlying protective plate member and is held in place by arivet. Consistently secure attachment of the thermostatic strip is thusassured, and the overlying plate member reduces the possibility ofdamage to the bimetallic strip. The overlying plate member extendsbeyond the end of the thermostatic strip and is there provided with anadjusting screw which allows more accurate adjustment of the tension inthe bimetallic strip. A tang depending from the overlying plate memberextends into a well of high viscosity silicone fluid within the valvemember to reduce vibrations of the valve member. The valve body andattached structure is enclosed within a protective casing member tofurther reduce its vulnerability to damage.

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The details as well as other objects and advantages of this inventionare shown in the drawing and disclosed in the description of a preferredembodiment.

SUMMARY OF THE DRAWING FIGURE 1 is a front elevational view of aninternal combustion engine which has an air cleaner and silencerassembly adapted to control the temperature of the induction air flow;

FIGURE 2 is a side elevational view of the air cleaner and silencerassembly with parts broken away to show the thermostatic control and theair flow control valve;

FIGURE 3 is a sectional view through the thermostatic controlillustrating all components, the section being taken generally alongline 33 of FIGURE 4; and

FIGURE 4 is a top plan view of the thermostatic control.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring first to FIGURE 1, aninternal combustion engine 10 includes an intake manifold 12 and acarburetor 14- on which an air cleaner and silencer assembly 16 ismounted. Intake manifold 12 and carburetor 14 form an induction passage18 (FIGURE 2) in which a throttle 20 is disposed to control the air flowto engine 10. Engine 10 also includes an exhaust manifold 22 whichdischarges through an exhaust pipe 24. A stove 26 is disposed abouteither exhaust manifold 22 or exhaust pipe 24 to provide a source ofheated air.

Referring to FIGURE 2, air cleaner and silencer assembly 16 defines asilencing chamber 28 within which an air filter element 29 is disposed.A flange 30 at the base of assembly 16 surrounds the outlet 31 andregisters with the inlet of carburetor 14. A tuned conduit or snorkel 32extends from a flared end 34, open to air at ambient or underhoodtemperatures, to an inlet 35 opening into chamber 28. Conduit 32 alsohas a lateral opening 36 to which a pipe 38 leads warmed air from stove26. A valve 40, pivoted at 42, may be swung between the position shown,where it prevents heated air flow through opening 36 by means of anextension 44, and a position preventing air flow through the open end 34of snorkel 32. In the position shown, only air at ambient temperaturemay be admitted to the engine, but as valve 40 rotates and extension 44-is moved from opening 36, increasing amounts of heated air anddecreasing amounts of ambient air are admitted and mixed to flow toengine 10.

Valve 40 is secured by a rod 46 to the diaphragm 48 of a vacuum motor 49and is biased to the position shown by a spring 50. As vacuum signalsabove about 6 Hg are applied to diaphragm 48 against the force of spring50, valve 40 is pivoted from the position shown to heat the inductionair flow above ambient temperatures.

A thermostatic control 52 is provided for supplying vacuum signalsthrough a line 54 to vacuum motor 49. As shown in detail in FIGURE 3,thermostatic control 52 has a chamber 56 which is subjected to thevacuum conditions existing in induction passage 18 below throttle 20.The vacuum in chamber 56 is modulated by air bled past a valve member 58which is positioned by a thermostatically responsive bimetallic strip60. Thermostatic control 52 is located within air cleaner chamber 28 sothat bimetallic strip 60 senses the temperature of the induction airflow. At low temperatures, the head 62 of valve member 58 is heldagainst its valve seat 64 to prevent air flow into chamber 56 throughthe orifice 66, and vacuum motor 49 then positions valve 40 solely inaccordance with variations in induction vacuum. Under these conditions,during wide open throttle operation the value of induction vacuum issufiiciently low that vacuum motor spring 50 moves valve 40 to theposition shown in FIG- URE 2 whereby only cool air is delivered to theengine for maximum power; during most modes of engine operation,however, valve blocks ambient air flow through open end 34 of conduit 32and heated air alone is admitted through lateral opening 36.

As the induction air flow temperature rises, bimetallic strip permitsvalve member 58 to open, and air admitted through orifice 66 reduces thevacuum in chamber 56. Valve 40 is then repositioned to reduce the flowof heated air through lateral opening 35 and increase the flow ofambient air through open end 34 of snorkel 32. In this way the inductionair flow temperature is maintained at a substantially uniform levelduring the low speed modes of engine operation.

As noted above, the construction of thermostatic control 52 is ofparticular interest. The details of this construction are shown inFIGURES 3 and 4. Thermostatic control 52 comprises a pair of cuppedmembers 68 and 70. The lateral wall 72 of lower member engages thelateral wall 74 of upper member 68 and is provided with a shoulder 76which receives the bottom wall 78 of upper member 68. The lateral wall74 of upper member 68 is crimped inwardly over lateral wall 72 of lowermember 70, as at 80. An annular seal or gasket 82 is located on shoulder76 beneath the upper member 68 to assure complete enclosure of chamber56 which is formed between cupped members 68 and 70.

The bottom wall 83 of lower member 70 has a pair of projections 84a and84b, each having a restricted aperture 85, which respectively defineinterchangeable inlet and outlet fittings for chamber 56. A line 87connects one fitting, 84a, for example, with induction passage 18 belowthrottle 20 while line 54 connects the other fitting, 8411, with vacuummotor 49.

Upper member 68 has a lateral projection 86 underlying bimetallic strip60, and a rivet 88 secures both metallic strip 60 and a rigid plate 90to projection 86. As shown in FIGURE 4, plate 90 extends forsubstantially the entire length of bimetallic strip 60 and forsubstantial distances on either side of bimetallic strip 60 to preventdamage to strip 60. An extension 92 of plate 90 reaches beyond the endof strip 60 and holds a threaded adjusting screw 94 which bears againstbottom wall 78 of upper cupped member 68. By turning adjusting screw 94,plate 90 and bimetallic strip 60 may be pivotally raised (and lowered)with respect to bottom wall 78 of upper member 68. The free end 96 ofbimetallic strip 60, which embraces the stem 98 of valve member 58 andreceives an enlargement 100 of stem 98, may thus be raised to increasethe force with which valve head 62 is held against its seat 64.

In order to damp vibrations of valve member 58, a tang 102 extends fromplate 90 into a recess or well 104 of high viscosity fluid 106, such asa silicon fluid having a viscosity on the order of 350,000 centistokes.This arrangement allows gradual adjustment of valve member 58 bythermostat 60, but prevents high frequency vibrations of valve member58.

For further protection, thermostatic control 52 includes a unitaryplastic outer casing 108. Casing 108 includes a lower portion 110 havingan annular shoulder 112, which receives shoulder 76 of lower cuppedmember 72, and an opening 114. which grips lateral wall 72 of lowermember 70. An upper portion 116 is secured on one side to lower portion110 by an integral hinge 118 and extends entirely over plate 90,thermostat 60, and valve member 58. On the opposite side, lower portion110 has a pair of pins 120 which extend through a pair of openings 122in upper portion 116 and which are riveted over as at 124 to securelyretain the casing about the remainder of control 52. Casing 108 thusreadily protects the operating components of control 52 to assureaccuracy in the performance of the control.

The advantages of this control in providing reliable operation may bereadily understood from the foregoing, and the simplicity in theconstruction of this control will be appreciated by those concerned withefforts to control product cost.

I claim:

1. A thermostatic control comprising upper and lower upwardly openingcupped members each having a bottom wall and a cylindrical lateral wall,the lateral wall of said lower member being formed to define an annularshoulder facing upwardly within said lower member, said lower memberreceiving said upper member therewithin whereby an upper portion of thelateral wall of said lower member engages the lateral wall of said uppermember and whereby said shoulder engages an annular portion of thebottom wall of said upper member to thereby define an enclosed chamberbetween said members, said lower member having an inlet fitting adaptedfor connection to a source of vacuum and forming a restricted apertureopening through said bottom wall of said lower member to said chamberfor supplying vacuum to said chamber, said lower member having anotherfitting adapted for connection to a vacuum responsive device and formingan opening through said bottom wall of said lower member from saidchamber for delivering vacuum signals to said device, said upper memberhaving an orifice opening through said bottom wall thereof into saidchamber for admitting air thereto to reduce the vacuum therein, thelower side of said upper member defining a valve seat surrounding saidorifice, a valve member cooperating with said valve seat to vary theflow of air through said orifice into said chamber and control thevacuum therein whereby vacuum signals are formed for delivery to saidvacuum responsive device, said valve member including a valve headdisposed in said chamber for engaging said seat and a valve stemextending upwardly from said head through said orifice, said valve stemhaving an enlargement at the upper end thereof, a thermally responsivestrip having one end receiving said valve stem and engaging the lowerside of said valve stem enlargement for supporting and positioning saidvalve member within said orifice and for exerting a force tending tolift said valve head into engagement with said valve seat which forcevaries in an inverse relationship with temperature variations, saidupper member having a lateral projection underlying the opposite end ofsaid strip, a rigid protective plate member overlying said strip toprevent damage thereto, means securing one end of said plate member tosaid lateral projection and clamping said opposite end of said striptherebetween, said valve stem enlargement having a recess in the topthereof, said recess containing a high viscosity damping fluid, and saidoverlying plate member having a projection extending downwardly intosaid fluid for damping vibration of said valve member whereby saidthermally responsive strip may position said valve member to preciselycontrol the vacuum within said chamber in accordance with temperatureconditions and whereby accurate vacuum signals may be delivered to saidvacuum responsive device.

2. The thermostatic control of claim 1 wherein the opposite end of saidprotective plate member extends beyond said one end of said thermallyresponsive strip and which further comprises an adjusting screwthreadedly received through said opposite end of said plate member andbearing against said bottom wall of said upper member whereby thespacing between said opposite end of said protective plate member andsaid bottom wall of said upper member may be varied to cause said rigidplate member and said strip and said lateral projection to pivot withrespect to said bottom wall of said upper member whereby the liftingforce exerted by said thermally responsive strip on said valve membermay be adjusted.

3. The thermostatic control of claim 1 or 2 which further includes aprotective casing comprising a lower portion having an annular walldefining an opening therethrough, said annular wall having a shoulderformed therein, said lower cupped member extending through said openingin said lower portion whereby said lateral wall of said lower memberengages said annular wall and whereby said shoulder of said lower memberengages said shoulder of said annular Wall, said protective casingfurther comprising an upper portion extending over said protective platemember and connected at one side thereof to one side of said lowerportion by an integral hinge portion, the opposite sides of said upperand lower portions respectively having cooperating opening and pin meansfor securing said opposite side of said upper portion to said oppositeside of said lower portion and thereby retaining said protective casingin place.

4. An air inlet assembly for an internal combustion engine having an airinduction passage and a throttle controlling flow through said inductionpassage, said assembly comprising a housing forming a silencing chamberand having an outlet opening from said chamber and adapted forregistration with said induction passage, said housing further having aninlet opening into said chamber and a tuned conduit extending to saidinlet, said tuned conduit having the end remote from said inlet open toair at ambient temperatures and having a lateral opening adapted forconnection to a source of air warmed to temperatures greater thanambient, ambient air flow admitted through said remote end and warmedair flow admitted through said lateral opening being mixed in saidconduit and said chamber to provide an induction air flow attemperatures greater than ambient, valve means disposed within saidconduit and controlling air flow through said remote end and throughsaid lateral opening to regulate the temperature of the induction airflow, spring means biasing said valve means to permit ambient air flowthrough said remote end and to prevent warmed air flow through saidlateral opening, a vacuum responsive device connected to said valvemeans for exerting a force on said valve means in opposition to the biasof said spring means in response to vacuum signals, and the thermostaticcontrol of claim 1 disposed within said assembly downstream of saidvalve means and responsive to temperatures of the induction air flow,said control having said inlet fitting adapted for connection to saidinduction passage below said throttle and said another fitting connectedto said vacuum responsive device for supplying vacuum signals theretowhereby said valve means may be positioned in accordance with theinduction air flow temperature.

References Cited UNITED STATES PATENTS 2,082,397 6/ 1937 Hiscock.2,763,252 9/1956 Dolza et al. 2,781,032 2/1957 Sebok et al. 2,868,4591/1959 Modes 23687 2,946,509 7/1960 Radtke et al. 23687 3,208,441 9/1965 Ottofy. 3,319,888 5/1967 Creager 23687 3,373,934 3/1968 Kolbe etal. 23613 3,394,687 7/1968 Scott 123122 X AL LAWRENCE SMITH, PrimaryExaminer US. Cl. X.R. 236-13, 87

